This invention relates generally to the testing of radar systems and, more particularly, to a method and system for testing radar systems employing phased-array antenna systems.
A phased-array system consists of a large number of identical radiating elements and phase-shifting elements. Because of this redundancy, failures of a few elements have little effect on the array performance. This graceful degradation feature is one of the advantages of a phased-array system. However, because of this phenomenon, it is very difficult to determine when the array has deteriorated to the extent that its performance is not acceptable. Furthermore, it is difficult to obtain an accurate assessment of the array performance during operation due to constant variations in environmental conditions and the complexity of the phased-array system. Nevertheless, it is often necessary to monitor the operating characteristics of a system to ensure that an acceptable level of performance is maintained. Defective elements must be detected so that they may be replaced at the earliest convenient time.
A number of monitoring techniques are applicable to any phased-array antenna. In the past, an array-monitoring system usually sampled the output of the phase-shifter driving network on the assumption that the phase shifters and the feed network are passive elements which seldom develop failures. However, a radio-frequency (rf) monitoring system which can detect any failure from the transmitter to the radiating array has clear advantages over systems which monitor the operation of selected components. Furthermore, with the development of limited-scanning antennas, the feed networks have become more complicated. Although passive networks are highly reliable, monitoring techniques which can detect failures in such networks are needed.